Low attenuation large effective area optical fiber

ABSTRACT

An optical waveguide fiber having a multi-segmented core surrounded by a cladding, the core having a central segment and an annular segment surrounding the central segment. The central segment has a positive relative refractive index profile, and the annular segment has a negative relative refractive index profile. The optical fiber exhibits an effective area of greater than about 75 μm 2  at a wavelength of about 1550 nm, a dispersion slope of less than 0.07 ps/nm 2 /km at a wavelength of about 1550 nm, a zero-dispersion wavelength of between about 1290 and 1330 nm, and an attenuation of less than 0.20 dB/km, and preferably less than 0.19 dB/km, at a wavelength of about 1550 nm.

This application is a continuation of U.S. patent application Ser. No.10/835,874 filed on Apr. 29, 2004 now U.S. Pat. No. 7,187,833, thebenefit of priority is hereby claimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to large effective area optical fibers.

2. Technical Background

Known fibers have optical characteristics which are suitable foroperation in specific windows. For example, standard single modetransmission fibers, such as the SMF-28™ optical fiber manufactured byCorning Incorporated, have a zero dispersion wavelength at or near 1310nm, and such fibers can perform suitably in the 1310 nm window. Thedispersion exhibited by such optical fiber at 1550 nm is around 17ps/nm/km. LEAF® fiber by Corning Incorporated which has an average zerodispersion wavelength near 1500 nm and a dispersion slope of about 0.08ps/nm/km at about 1550 nm.

SUMMARY OF THE INVENTION

Disclosed herein is an optical waveguide fiber-having a multi-segmentedcore surrounded by a cladding, the core comprising a central segmentextending radially outwardly from the centerline and an annular segmentsurrounding the central segment. The central segment preferably has apositive relative refractive index profile, and the annular segmentpreferably has a negative relative refractive index profile. The opticalfiber exhibits an effective area of greater than about 80 μm² at awavelength of about 1550 nm, a dispersion slope of less than 0.07ps/nm²/km at a wavelength of about 1550 nm, a zero-dispersion wavelengthof between about 1290 and 1330 nm, and an attenuation of less than 0.20dB/km, and preferably less than 0.19 dB/km, at a wavelength of about1550 nm. Preferably, the dispersion is greater than 15 ps/nm-km, morepreferably between 15 and 21 ps/nm-km, even more preferably between 16and 20 ps/nm-km.

Preferably, the central segment has an alpha profile with an α1preferably less than 4, more preferably less than 3, and in somepreferred embodiments, α1 is between 1 and 3, and in other preferredembodiments, α1 is less than 1.

In some preferred embodiments, the annular segment surrounds and isdirectly adjacent to the central segment. In other preferredembodiments, the core further comprises an intermediate annular segmentdisposed between the central segment and the annular segment, whereinthe intermediate annular segment surrounds and is directly adjacent tothe central segment, and wherein the annular segment surrounds and isdirectly adjacent to the intermediate annular segment. Preferably, theintermediate annular segment has a relative refractive index profilehaving a maximum absolute magnitude, |Δ|, less than 0.05%, morepreferably less than 0.02%, and even more preferably equal to 0.00%.

In preferred embodiments, the optical fiber disclosed herein has anattenuation at 1380 nm not more than 0.1 dB/km greater than anattenuation at 1310 nm. Preferably, the attenuation at 1380 nm isless-than the attenuation at 1310 nm.

Preferably the optical fiber described and disclosed herein allowssuitable performance at a plurality of operating wavelength windowsbetween about 1260 nm and about 1650 nm. More preferably, the opticalfiber described and disclosed herein allows suitable performance at aplurality of wavelengths from about 1260 nm to about 1650 nm. In apreferred embodiment, the optical fiber described and disclosed hereinis a dual window fiber which can accommodate operation in at least the1310 nm window and the 1550 nm window.

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a refractive index profile corresponding to a first set ofpreferred embodiments of an optical waveguide fiber as disclosed herein.

FIG. 2 shows refractive index profiles corresponding to a second set ofpreferred embodiments of an optical waveguide fiber as disclosed herein.

FIG. 3 shows refractive index profiles corresponding to third and fourthsets5 of preferred embodiments of an optical waveguide fiber asdisclosed herein.

FIG. 4 is a schematic cross-sectional view of a preferred embodiment ofan optical waveguide fiber as disclosed herein.

FIG. 5 is a schematic illustration of a fiber optic communication systememploying an optical fiber as disclosed herein.

FIG. 6 schematically illustrates another embodiment of an optical fibercommunication system disclosed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Additional features and advantages of the invention will be set forth inthe detailed description which follows and will be apparent to thoseskilled in the art from the description or recognized by practicing theinvention as described in the following description together with theclaims and appended drawings.

The “refractive index profile” is the relationship between refractiveindex or relative refractive index and waveguide fiber radius.

The “relative refractive index percent” is defined as Δ%=100×(n_(i)^(2−n) _(c) ²)/2n_(i) ², where n_(i) is the maximum refractive indexregion i, unless otherwise specified, and n_(c) is the averagerefractive index of the cladding region. As used herein, the relativerefractive index is represented by Δ and its values are given in unitsof “%”, unless otherwise specified. In cases where the refractive indexof a region is less than the average refractive index of the claddingregion, the relative index percent is negative and is referred to ashaving a depressed region or depressed index, and is calculated at thepoint at which the relative index is most negative unless otherwisespecified. In cases where the refractive index of a region is greaterthan the average refractive index of the cladding region, the relativeindex percent is positive and the region can be said to be raised or tohave a positive index. An “updopant” is herein considered to be a dopantwhich has a propensity to raise the refractive index relative to pureundoped SiO₂. A “downdopant” is herein considered to be a dopant whichhas a propensity to lower the refractive index relative to pure undopedSiO₂. An updopant may be present in a region of an optical fiber havinga negative relative refractive index when accompanied by one or moreother dopants which are not updopants. Likewise, one or more otherdopants which are not updopants may be present in a region of an opticalfiber having a positive relative refractive index. A downdopant may bepresent in a region of an optical fiber having a positive relativerefractive index when accompanied by one or more other dopants which arenot downdopants. Likewise, one or more other dopants which are notdowndopants may be present in a region of an optical fiber having anegative relative refractive index.

“Chromatic dispersion”, herein referred to as “dispersion” unlessotherwise noted, of a waveguide fiber is the sum of the materialdispersion, the waveguide dispersion, and the inter-modal dispersion. Inthe case of single mode waveguide fibers the inter-modal dispersion iszero. Zero dispersion wavelength is a wavelength at which the dispersionhas a value of zero. Dispersion slope is the rate of change ofdispersion with respect to wavelength.

“Effective area” is defined as:A _(eff)=27π(∫f ² r dr)²/(∫f ⁴ r dr),

where the integration limits are 0 to ∞, and f is the transversecomponent of the electric field associated with light propagated in thewaveguide. A used herein, “effective area” or A_(eff) refers to opticaleffective area at a wavelength of 1550 nm unless otherwise noted.

The term “α-profile” refers to a relative refractive index profile,expressed in terms of Δ(r) which is in units of “%”, where r is radius,which follows the equation,Δ(r)=Δ(r _(o)) (1−[|r−r _(o)|/(r ₁ −r _(o))]^(α)),where r_(o) is the point at which Δ(r) is maximum, r₁ is the point atwhich Δ(r) % is zero, and r is in the range r_(i)≦r≦r_(f), where Δ isdefined above, r_(i) is the initial point of the α-profile, r_(f) is thefinal point of the α-profile, and α is an exponent which is a realnumber.

The mode field diameter (MFD) is measured using the Peterman II methodwherein, 2w=MFD, and w²=(2∫f² r dr/∫[df/dr]² r dr), the integral limitsbeing 0 to ∞.

The bend resistance of a waveguide fiber can be gauged by inducedattenuation under prescribed test conditions.

One type of bend test is the lateral load microbend test. In thisso-called “lateral load” test, a prescribed length of waveguide fiber isplaced between two flat plates. A#70 wire mesh is attached to one of theplates. A known length of waveguide fiber is sandwiched between theplates and a reference attenuation is measured while the plates arepressed together with a force of 30 newtons. A 70 newton force is thenapplied tot he plates and the increase in attenuation in dB/m ismeasured. The increase in attenuation is the lateral load attenuation ofthe waveguide.

The “pin array” bend test is used to compare relative resistance ofwaveguide fiber to bending. To perform this test, attenuation loss ismeasured for a waveguide fiber with essentially no induced bending loss.The waveguide fiber is then woven about the pin array and attenuationagain measured. The loss induced by bending is the difference betweenthe two measured attenuations. The pin array is a set of ten cylindricalpins arranged in a single row and held in a fixed vertical position on aflat surface. The pin spacing is 5 mm, center to center. The pindiameter is 0.67 mm. During testing, sufficient tension is applied tomake the waveguide fiber conform to a portion of the pin surface.

The theoretical fiber cutoff wavelength, or “theoretical fiber cutoff”,or “theoretical cutoff”, for a given mode, is the wavelength above whichguided light cannot propagate in that mode. A mathematical definitioncan be found in Single Mode Fiber Optics, Jeunhomme, pp. 39-44, MarcelDekkeri, N.Y., 1990 wherein the theoretical fiber cutoff is described asthe wavelength at which the mode propagation constant becomes equal tothe plane wave propagation constant in the outer cladding. Thistheoretical wavelength is appropriate for an infinitely long, perfectlystraight fiber that has no diameter variations.

The effective fiber cutoff is lower than the theoretical cutoff due tolosses that are induced by bending and/or mechanical pressure. In thiscontext, the cutoff refers to the higher of the LP11 and LP02 modes.LP11 and LP02 are generally not distinguished in measurements, but bothare evident as steps in the spectral measurement, i.e. no power isobserved in the mode at wavelengths longer than the measured cutoff. Theactual fiber cutoff can be measured by the standard 2 m fiber cutofftest, FOTP-80 (EIA-TIA-455-80), to yield the “fiber cutoff wavelength”,also known as the “2 m fiber cutoff” or “measured cutoff”. The FOTP-80standard test is performed to either strip out the higher order modesusing a controlled amount of bending, or to normalize the spectralresponse of the fiber to that of a multimode fiber.

The cabled cutoff wavelength, or “cabled cutoff” is even lower than themeasured fiber cutoff due to higher levels of bending and mechanicalpressure in the cable environment. The actual cabled condition can beapproximated by the cabled cutoff test described in the EIA-445 FiberOptic Test Procedures, which are part of the EIA-TIA Fiber OpticsStandards, that is, the Electronics Industry Alliance—TelecommunicationsIndustry Association Fiber Optics Standards, more commonly known asFOTP's. Cabled cutoff measurement is described in EIA-455-170 CableCutoff Wavelength of Single-mode Fiber by Transmitted Power, or“FOTP-170”.

Unless otherwise noted herein, optical properties (such as dispersion,dispersion slope, etc.) are reported for the LP01 mode.

A waveguide fiber telecommunications link, or simply a link, is made upof a transmitter of light signals, a receiver of light signals, and alength of waveguide fiber or fibers having respective ends opticallyconnected to the transmitter and receiver to propagate light signalstherebetween. The length of waveguide fiber can be made up of aplurality of shorter lengths that are spliced or connected together inend to end series arrangement. A link can include additional opticalcomponents such as optical amplifiers, optical attenuators, opticalisolators, optical switches, optical filters, or multiplexing ordemultiplexing devices. One may denote a group of inter-connected linksas a telecommunications system.

A span of optical fiber as used herein includes a length of opticalfiber, or a plurality of optical fibers fused together serially,extending between optical devices, for example between two opticalamplifiers, or between a multiplexing device and an optical amplifier. Aspan may comprise one or more sections of optical fiber as disclosedherein, and may further comprise one or more sections of other opticalfiber, for example as selected to achieve a desired system performanceor parameter such as residual dispersion at the end of a span.

Various wavelength bands, or operating wavelength ranges, or wavelengthwindows, can be defined as follows: “1310 nm band” is 1260 to 1360 nm;“E-band” is 1360 to 1460 nm; “S-band” is 1460 to 1530 nm; “C-band” is1530 to 1565 nm; “L-band” is 1565 to 1625 mm; and “U-band” is 1625 to1675 nm.

The optical fiber disclosed herein comprises a core and a cladding layer(or cladding) surrounding and directly adjacent the core. The claddinghas a refractive index profile, Δ_(CLAD)(r). Preferably, Δ_(CLAD)(r)=0throughout the cladding. The core comprises a refractive index profile,Δ_(CORE)(r). The core is comprised of a plurality of core segments, eachhaving respective refractive index profiles.

Preferably, the central segment comprises silica doped with germanium,i.e. germania doped silica. Dopants other than germanium, singly or incombination, may be employed within the core, and particularly at ornear the centerline, of the optical fiber disclosed herein to obtain thedesired refractive index and density.

Preferably, the refractive index profile of the optical fiber disclosedherein is non-negative from the centerline to the inner radius of theannular segment, which is either R₁ for embodiments without anintermediate annular segment, or which is the inner radius of theannular segment is R₂ for embodiments with an intermediate annularsegment. In preferred embodiments, the optical fiber contains noindex-decreasing dopants in the central segment.

In a first group of embodiments, optical waveguide fibers 100 aredisclosed herein which preferably comprise: a central segment 20extending radially outwardly from the centerline to a central segmentouter radius, R₁, and having a relative refractive index profile, Δ₁(r)in %, with a maximum relative refractive index percent, Δ_(1MAX), anintermediate annular segment 30 surrounding the central segment 20 anddirectly adjacent thereto, extending radially outwardly to anintermediate annular segment outer radius, R₂, having a width W₂disposed at a midpoint R_(2MID), and having a relative refractive indexprofile, Δ₂(r) in %, with a maximum absolute magnitude relativerefractive index percent, |Δ_(2MAX)|; an annular segment 50 surroundingthe intermediate annular segment 30 and preferably directly adjacentthereto, and extending radially outwardly from R₂ to an annular segmentouter radius, R₃, and having a width W₃ disposed at a midpoint R_(3MID),and having a relative refractive index profile, Δ₃(r) in %, with aminimum relative refractive index percent, Δ_(3MIN), whereinΔ_(1MAX)>0>Δ_(3MIN); and an outer annular cladding 200 surrounding theannular segment 50 and preferably directly adjacent thereto and having arelative refractive index percent, Δ_(CLAD)(r) in %. R₁ is defined tooccur at the intersection with the horizontal Δ(r)=0% axis of a line 21drawn tangent to the point on Δ₁(r) corresponding to the quarter peakheight (Δ_(1MAX)/4) of the central segment, the quarter peak heightoccurring at a radius R_(1QH). R₂ is defined to occur at theintersection with the horizontal Δ(r)=0% axis of a line drawn tangent tothe point on Δ₃(r) corresponding to an inner half peak height(Δ_(3MIN)/2) of the annular segment, the inner half peak heightoccurring at a radius R_(3HHI). The intermediate annular segment 30begins at R₁ and ends at R₂, and the annular segment 50 begins at R₂ andends at R₃ for this group of embodiments. R₃ is defined to occur at theintersection with the horizontal Δ(r)=0% axis of a line drawn tangent tothe point on Δ₃(r) corresponding to an outer half peak height(Δ_(3MIN)/2) of the annular segment, the outer half peak heightoccurring at a radius R_(3HHO). The half-height peak width of theannular segment, HHPW3, is R_(3HHO)−R_(3HHI), and the midpoint of thehalf-height peak width of the annular segment, R_(3HHMID), is(R_(3HHI)+R_(3HHO))/2. The width W₃ of the annular segment is R₃−R₂ andits midpoint R_(3MID) is (R₂+R₃)/2. Preferably, more than 90% of theradial width of the central segment has a positive relative refractiveindex, more preferably Δ₁(r) is positive for all radii from 0 to R₁.Preferably, |Δ_(2MAX)|<0.05%, more preferably |Δ_(2MAX)|<0.025%, andeven more preferably |Δ_(2MAX)|0.0% for more than 90% of the radialwidth of the intermediate annular segment, even more preferably for allradii from R₁ to R₂. Preferably, more than 90% of the radial width ofthe annular segment has a negative relative refractive index, morepreferably Δ₃(r) is negative for all radii from R₁ to R₃. Preferably,Δ_(CLAD)(r) is zero for all radii from R₃ to the outermost radius of thecladding 200, i.e. the outermost diameter of the silica-based part ofthe optical fiber (excluding any coating). The core ends and thecladding begins at a radius R_(CORE), and preferably R_(CORE)=R₃.

In a second group of embodiments, optical waveguide fibers 100 aredisclosed herein which preferably comprise: a central segment 20extending radially outwardly from the centerline to a central segmentouter radius, R₁, and having a relative refractive index profile, Δ₁(r)in %, with a maximum relative refractive index percent, Δ_(1MAX); afirst annular segment (or moat) 30 surrounding the central segment 20and directly adjacent thereto, extending radially outwardly to a firstannular segment outer radius, R₂, having a width W₂ disposed at midpointR_(2MID), and having a non-negative relative refractive index percent,Δ₂ % (r) with a minimum relative refractive index percent, Δ_(2MIN),where Δ₂% (r)≧0; an annular segment 50 surrounding the central segment20 and preferably directly adjacent thereto, and extending radiallyoutwardly from R₁ to an annular segment outer radius, R₃, and having awidth W₃ disposed at a midpoint R_(3MID), and having a relativerefractive index profile, Δ₃(r) in %, with a minimum relative refractiveindex percent, Δ_(3MIN), wherein Δ_(1MAX)>0>Δ_(3MIN); and an outerannular cladding 200 surrounding the annular segment 50 and preferablydirectly adjacent thereto and having a relative refractive indexpercent, Δ_(CLAD)(r) in %. R₁ is defined to occur at the intersectionwith the horizontal Δ(r)=0% axis of a line 21 drawn tangent to the pointon Δ₁(r) corresponding to the quarter peak height (Δ_(1MAX)/4) of thecentral segment, the quarter peak height occurring at a radius R_(1QH).The annular segment 50 begins at a radius R₂, wherein R₂=R₁ for thisgroup of embodiments. R₃ is defined to occur at the intersection withthe horizontal Δ(r)=0% axis of a line drawn tangent to the point onΔ₃(r) corresponding to an outer half peak height (Δ_(3MIN)/2) of theannular segment, the outer half peak height occurring at a radiusR_(3HHO). An inner half peak height (Δ_(3MIN)/2) of the annular segmentoccurs at a radius R_(3HHI). The half-height peak width of the annularsegment, HHPW3, is R_(3HHO)−R_(3HHI), and the midpoint of thehalf-height peak width of the annular segment, R_(3HHMID), is (R₃_(HHI)+R_(3HHO))/2. The width W₃ of the annular segment is R₃−R₂ and itsmidpoint R_(3MID) is (R₂+R₃)/2. Preferably, more than 90% of the radialwidth of the central segment has a positive relative refractive index,more preferably Δ₁(r) is positive for all radii from 0 to R₁.Preferably, more than 90% of the radial width of the annular segment hasa negative relative refractive index, more preferably Δ₃(r) is negativefor all radii from R₁ to R₃. Preferably, Δ_(CLAD)(r) is zero for allradii from R₃ to the outermost radius of the cladding 200, i.e. theoutermost diameter of the silica-based part of the optical fiber(excluding any coating). The core ends and the cladding begins at aradius R_(CORE), and preferably R_(CORE)=R₃.

In some embodiments, the central segment of the core may comprise arelative refractive index profile having a so-called centerline dipwhich may occur as a result of one or more optical fiber manufacturingtechniques. For example, the central segment may have local minimum inthe refractive index profile at radii less than 1 μm, wherein highervalues for the relative refractive index (including the maximum relativerefractive index or the core segment) occur at radii greater than r=0μm. However, the centerline dip any of the refractive index profilesdisclosed herein is optional.

1^(st) Set of Preferred Embodiments

Tables 1-2 list characteristics of an illustrative first set ofpreferred embodiments, Examples 1-6. FIG. 1 shows the refractive indexprofiles corresponding to Examples 1-6, labeled as curve 1.

TABLE 1 Example 1 2 3 4 5 6 Δ_(1MAX) % 0.38 0.40 0.35 0.37 0.37 0.36R_(1QH) μm 5.2 5.1 5.4 4.8 5.8 5 R₁ μm 6.1 5.9 6.3 5.5 6.8 5.8 α₁ 2 2 22 2 2 |Δ₂|_(MAX) % 0 0 0 0 0 0 R₂ μm 12.3 12.2 12.6 11.5 13.4 13.3 W₂ μm6.2 6.3 6.3 6 6.6 7.5 R_(2MID) μm 9.2 9.05 9.45 8.5 10.1 9.55 Δ_(3MIN) %−0.1 −0.1 −0.1 −0.1 −0.1 −0.1 R_(3HHI) μm 12.5 12.3 12.7 11.6 13.5 13.4R_(3HHO) μm 19.2 19.5 19.5 18.7 20.5 20.5 HHPW3 μm 6.7 7.2 6.8 7.1 7 7.1R_(3HHMID) μm 15.85 15.9 16.1 15.15 17 16.95 R₃ = R_(CORE) μm 19.3 19.619.6 18.8 20.6 20.6 W₃ μm 7 7.4 7 7.3 7.2 7.3 R_(3MID) μm 15.8 15.9 16.115.15 17 16.95

TABLE 2 Example 1 2 3 4 5 6 Lambda Zero nm 1313 1316 1310 1324 1303 1320Dispersion @ 1310 nm ps/nm-km −0.3 −0.6 0.0 −1.3 0.6 −0.9 Slope @ 1310nm ps/nm²-km 0.090 0.090 0.090 0.090 0.091 0.089 Aeff @ 1310 nm μm² 69.065.1 73.3 65.3 74.7 68.8 MFD @ 1310 nm μm 9.52 9.26 9.82 9.31 9.87 9.54Attenuation @ 1310 nm dB/km 0.333 0.334 0.332 0.334 0.332 0.333Dispersion @ 1550 nm ps/nm-km 17.4 17.0 17.7 16.4 18.5 16.7 Slope @ 1550nm ps/nm²-km 0.062 0.062 0.062 0.063 0.062 0.062 Aeff @ 1550 nm μm² 88.283.6 93.8 85.7 93.5 90.0 MFD @ 1550 nm μm 10.85 10.56 11.18 10.73 11.1210.99 Attenuation @ 1550 nm dB/km 0.187 0.188 0.187 0.188 0.187 0.187Pin Array @ 1550 nm dB 10 8 14 22 4 21 Lateral Load @ 1550 nm dB/m 0.60.4 1.0 1.0 0.4 1.1 Fiber Cutoff nm 1440 1448 1437 1336 1595 1373 CableCutoff nm 1290 1298 1287 1186 1445 1223

The optical waveguide fiber in the first set of embodiments, such asExamples 1-6, comprises a central segment 20, an intermediate annularsegment 30, and an annular segment 50. Preferably Δ₁(r) for the centralsegment has an α-profile, more preferably the central segment has anα-profile with an α₁ less than 4, more preferably less than 3, even morepreferably between 1 and 3, and in some preferred embodiments between1.5 and 2.5.

Δ_(1MAX) is greater than 0.3%, preferably between 0.3 and 0.6%, morepreferably between 0.3 and 0.5%, even more preferably between 0.3 and0.4%, and R₁ is between 4 and 8 μm, more preferably between 5 and 7 μm.R₂ is between 10 and 15 μm, more preferably between 11 and 14 μm, W₂ isbetween 5 and 8 μm, more preferably between 5.5 and 7.5 μm, even morepreferably between 6 and 7 μm, and R_(2MID) is between 8 and 11 μm, morepreferably between 8.5 and 10.5 μm, even more preferably between 9 and10 μm. Δ_(3MIN) is less than −0.05% (that is, a greater absolutemagnitude but more negative than −0.05%), preferably between −0.05% and−0.15%, more preferably between −0.07 and −0.13%. In some preferredembodiments, Δ_(3MIN)=−0.1%. R₃ is between 17 and 22 μm, more preferablybetween 18 and 21 μm, W₃ is between 6 and 9 μm, more preferably between6.5 and 8.5 μm, even more preferably between 7 and 8 μm, and R_(3MID) isbetween 14 and 19 μm, more preferably between 15 and 18 μm, even morepreferably between 15 and 17 μm. The HHPW3 is between 5 and 9 μm, morepreferably between 6 and 8 μm.

The first set of embodiments have: lambda zero (zero dispersionwavelength) less than 1350 nm, preferably between 1290 and 1350 nm, morepreferably between 1290 and 1330; dispersion at 1310 nm between −5 and 5ps/nm-km, and in some preferred embodiments between −3 and 3 ps/nm-km;dispersion slope at 1310 nm less than 0.10 ps/nm²-km, preferably lessthan 0.095 ps/nm²-km; optical effective area at 1310 nm greater than 60μm², preferably greater than 65 μm², and in some preferred embodimentsbetween 65 and 80 μm²; MFD at 1310 nm greater than 9 μm, and in somepreferred embodiments between 9 and 10 μm; attenuation at 1310 nm ofless than 0.35 dB/km, preferably less than 0.34 dB/km; dispersion at1550 nm greater than 15 ps/nm-km, preferably between 15 and 21 ps/nm-km,more preferably between 16 and 20, and in some preferred embodimentsbetween 16 and 19 ps/nm-km; dispersion slope at 1550 nm less than 0.07ps/nm²-km, and in some preferred embodiments between 0.060 and 0.070ps/nm²-km; optical effective area at 1550 nm greater than 75 μm²,preferably greater than 80 μm², and in some preferred embodimentsbetween 80 and 100 μm²; MFD at 1550 nm greater than 10 μm, preferablygreater than 10.5 μm, and in some preferred embodiments between 10.5 and11.5 μm; attenuation at 1550 nm of less than 0.20 dB/km, preferably lessthan 0.19 dB/km; cable cutoff less than 1500 nm, preferably less than1400 nm, more preferably less than 1300 nm, and in some preferredembodiments between 1280 and 1300 nm. Preferably, the pin array loss at1550 nm is less than 25 dB, more preferably less than 20 dB, even morepreferably less than 15 dB, and in some preferred embodiments less than10 dB. Preferably the lateral load loss at 1550 nm is less than 2 dB/m,more preferably less than 1 dB/m, and in some preferred embodiments lessthan 0.5 dB/m. Preferably the fiber cutoff is less than 1500 nm, morepreferably less than 1450 nm, and in some preferred embodiments between1300 and 1450 nm.

2^(nd) Set of Preferred Embodiments

Tables 3-4 list characteristics of illustrative second set of preferredembodiments, Examples 7-8. FIG. 2 shows the refractive index profilescorresponding to Examples 7-8, labeled as curves 2A and 2B,respectively.

TABLE 3 Example 7 8 Δ_(1MAX) % 0.36 0.32 R_(1QH) μm 5 6 R₁ μm 5.8 7.1 α₁2 2 |Δ₂|_(MAX) % 0 0 R₂ μm 13.3 12.3 W₂ μm 7.5 5.2 R_(2MID) μm 9.55 9.7Δ_(3MIN) % −0.3 −0.2 R_(3HHI) μm 13.5 12.5 R_(3HHO) μm 20.5 25 HHPW3 μm7 12.5 R_(3HHMID) μm 17 18.75 R₃ = R_(CORE) μm 20.6 25.1 W₃ μm 7.3 12.8R_(3MID) μm 16.95 18.7

TABLE 4 Example 7 8 Lambda Zero nm 1319 1301 Dispersion @ 1310 nmps/nm-km −0.8 1.0 Slope @ 1310 nm ps/nm2-km 0.090 0.092 Aeff @ 1310 nmμm2 68.8 85.0 MFD @ 1310 nm μm 9.54 10.54 Attenuation @ 1310 nm dB/km0.333 0.331 Dispersion @ 1550 nm ps/nm-km 17.0 19.2 Slope @ 1550 nmps/nm2-km 0.064 0.064 Aeff @ 1550 nm μm2 89.5 106.2 MFD @ 1550 nm μm10.95 11.84 Attenuation @ 1550 nm dB/km 0.187 0.185 Pin Array @ 1550 nmdB 14 8 Lateral Load @ 1550 nm dB/m 0.7 0.9 Fiber Cutoff nm 1749 2008Cable Cutoff nm 1599 1858

The optical waveguide fiber in the second set of embodiments, such asExamples 7 and 8, comprises a central segment 20, an intermediateannular segment 30, and an annular segment 50. Preferably Δ₁(r) for thecentral segment has an α-profile, more preferably the central segmenthas an α-profile with an α₁ less than 4, more preferably less than 3,even more preferably between 1 and 3, and in some preferred embodimentsbetween 1.5 and 2.5.

Δ_(1MAX) is greater than 0.3%, preferably between 0.3 and 0.6%, morepreferably between 0.3 and 0.5%, even more preferably between 0.3 and0.4%, and R₁ is between 4 and 8 μm, more preferably between 5 and 7.5μm. R₂ is between 10 and 15 μm, more preferably between 12 and 14 μm, W₂is between 5 and 8 μm, and R_(2MID) is between 8 and 11 μm, morepreferably between 9 and 10 μm, Δ_(3MIN) is less than −0.15%, preferablybetween −0.15% and −0.4%, more preferably between −0.15 and −0.35%. Insome preferred embodiments, Δ_(3MIN) is less than or equal to −0.2 andis greater than or equal to −0.3%. R₃ is between 19 and 27 μm, morepreferably between 20 and 26 μm, W₃ is between 6 and 14 μm, morepreferably between 7 and 13 μm, and R_(3MID) is between 15 and 20 μm,more preferably between 16 and 19 μm. The HHPW3 is between 5 and 13 μm,more preferably between 6 and 12 μm.

The second set of embodiments have: lambda zero (zero dispersionwavelength) less than 1350 nm, preferably between 1290 and 1350 nm, morepreferably between 1290 and 1330, and in some preferred embodimentsbetween 1300 and 1320 nm; dispersion at 1310 nm between −5 and 5ps/nm-km, preferably between −3 and 3 ps/nm-km, and in some preferredembodiments between −2 and 2 ps/nm-km; dispersion slope at 1310 nm lessthan 0.10 ps/nm²-km, preferably less than 0.095 ps/nm²-km; opticaleffective area at 1310 nm greater than 60 μm², preferably greater than65 μm², and in some preferred embodiments greater than 80 μm², and inother preferred embodiments between 65 and 90 μm²; MFD at 1310 nmgreater than 9 μm, and in some preferred embodiments between 9 and 11μm; attenuation at 1310 nm of less than 0.35 dB/km, preferablyless than0.34 dB/km; dispersion at 1550 nm greater than 15 ps/nm-km, preferablybetween 15 and 21 ps/nm-km, more preferably between 16 and 20, and insome preferred embodiments between 17 and 19.5 ps/nm-km; dispersionslope at 1550 nm less than 0.07 ps/nm²-km, and in some preferredembodiments between 0.060 and 0.070 ps/nm²-km; optical effective area at1550 nm greater than 75 μm², preferably greater than 80 μm², morepreferably greater than 85 μm², and in some preferred embodimentsbetween 85 and 110 μm²; MFD at 1550 nm greater than 10 μm, preferablygreater than 10.5 μm, and in some preferred embodiments between 10.5 and12 μm; attenuation at 1550 nm of less than 0.20 dB/km, preferably lessthan 0.19 dB/km. In some embodiments, the cable cutoff is less than 1900nm, and in other embodiments less than 1600 nm. Preferably, the pinarray loss at 1550 nm is less than 25 dB, more preferably less than 20dB, even more preferably less than 15 dB, and in some preferredembodiments less than 10 dB. Preferably the lateral load loss at 1550 nmis less than 2 dB/m, more preferably less than 1 dB/m. Preferably thefiber cutoff is less than 1800 nm, more preferably less than 1700 nm.

3^(rd) and 4^(th) Sets of Preferred Embodiments

An illustrative third set of preferred embodiments is represented byExample 9 in Tables 5-6 and by the refractive index profile labeledcurve 4 in FIG. 3. An illustrative fourth set of preferred embodimentsis represented by Example 10 in Tables 5-6 and by the refractive indexprofile labeled curve 5 in FIG. 3.

TABLE 5 Example 9 10 Δ_(1MAX) % 0.44 0.58 R_(1QH) μm 5.9 4.4 R₁ μm 7.17.3 α₁ 1.6 0.4 |Δ₂|_(MAX) % 0 (n/a) R₂ μm 8.9 7.3 W₂ μm 1.8 0 R_(2MID)μm 8 7.3 Δ_(3MIN) % −0.15 −0.2 R_(3HHI) μm 9 8 R_(3HHO) μm 14 15 HHPW3μm 5 7 R_(3HHMID) μm 11.5 11.5 R₃ = R_(CORE) μm 14.1 15.1 W₃ μm 5.2 7.8R_(3MID) μm 11.5 11.2

TABLE 6 Example 9 10 Lambda Zero nm 1301 1318 Dispersion @ 1310 nmps/nm-km 0.8 −0.8 Slope @ 1310 nm ps/nm2-km 0.094 0.099 Aeff @ 1310 nmμm2 68.3 65.9 MFD @ 1310 nm μm 9.43 9.37 Attenuation @ 1310 nm dB/km0.332 0.331 Dispersion @ 1550 nm ps/nm-km 19.3 18.6 Slope @ 1550 nmps/nm2-km 0.064 0.067 Aeff @ 1550 nm μm2 84.2 84.8 MFD @ 1550 nm μm10.51 10.61 Attenuation @ 1550 nm dB/km 0.187 0.186 Pin Array @ 1550 nmdB 1 19 Lateral Load @ 1550 nm dB/m 0.1 0.8 Fiber Cutoff nm 1627 1516Cable Cutoff nm 1477 1366

The optical waveguide fiber in the third set of embodiments, such asExample 9, comprises a central segment 20, an intermediate annularsegment 30, and an annular segment 50. Preferably Δ₁(r) for the centralsegment has an α-profile, more preferably the central segment has anα-profile with an α₁ less than 3, more preferably less than 2, even morepreferably between 1 and 2, and in some preferred embodiments between1.4 and 1.8.

Δ_(1MAX) is greater than 0.3%, preferably greater than 0.4%, morepreferably between 0.4 and 0.5%, and R₁ is between 6 and 8 μm. R₂ isbetween 8 and 10 μm, W₂ is between 1 and 3 μm, and R_(2MID) is between 7and 9 μm. Δ_(3MIN) is less than −0.1%, preferably between −0.1% and−0.2%. R₃ is between 11 and 17 μm, more preferably between 13 and 15 μm,W₃ is between 3 and 7 μm, more preferably between 4 and 6 μm, andR_(3MID) is between 10 and 13 μm, more preferably between 11 and 12 μm.The HHPW3 is between 4 and 6 μm.

The third set of embodiments have: lambda zero (zero dispersionwavelength) less than 1350 nm, preferably between 1290 and 1350 nm, morepreferably between 1290 and 1330; dispersion at 1310 nm between −5 and 5ps/nm-km, preferably between −3 and 3 ps/nm-km, and in some preferredembodiments between −2 and 2 ps/nm-km; dispersion slope at 1310 nm lessthan 0.10 ps/nm²-km, preferably less than 0.095 ps/nm²-km; opticaleffective area at 1310 nm greater than 60 μm², preferably greater than65 μm²; MFD at 1310 nm greater than 9 μm, and in some preferredembodiments between 9 and 11 μm; attenuation at 1310 nm of less than0.35 dB/km, preferably less than 0.34 dB/km; dispersion at 1550 nmgreater than 15 ps/nm-km, preferably between 15 and 21 ps/nm-km, morepreferably between 16 and 20; dispersion slope at 1550 nm less than 0.07ps/nm²-km, and in some preferred embodiments between 0.060 and 0.070ps/nm²-km; optical effective area at 1550 nm greater than 75 μm²,preferably greater than 80 μm², and in some preferred embodimentsbetween 85 and 95 μm²; MED at 1550 nm greater than 10 μm, and in somepreferred embodiments between 10 and 11 μm; attenuation at 1550 nm ofless than 0.20 dB/km, preferably less than 0.19 dB/km. In someembodiments, the cable cutoff is less than 1500 nm, and in otherembodiments between 1300 and 1500 nm. Preferably, the pin array loss at1550 nm is less than 25 dB, more preferably less than 20 dB, even morepreferably less than 15 dB, still more preferably less than 10 dB, andin some preferred embodiments less than 5 dB. Preferably the lateralload loss at 1550 nm is less than 2 dB/m, more preferably less than 1dB/m. Preferably the fiber cutoff is less than 1650, more preferablyless than 1550 nm.

The optical waveguide fiber in the fourth set of embodiments, such asExample 10, comprises a central segment 20 and an annular segment 50surrounding and directly adjacent to the central segment 20. PreferablyΔ₁(r) for the central segment has an α-profile, more preferably thecentral segment has an α-profile with an α₁, less than 1, even morepreferably between 0.1 and 1, still more preferably between 0.25 and0.75, and in some preferred embodiments between 0.3 and 0.6.

Δ_(1MAX) is greater than 0.4%, preferably greater than 0.5%, morepreferably between 0.5 and 0.65%, and R₁ is between 6 and 8 μm. R₂ isbetween 6 and 9 μm, preferably between 7 and 8 μm. W₂ is 0 because anintermediate annular segment is absent. Δ_(3MIN) is less than −0.1%,preferably between −0.1% and −0.3%. R₃ is between 12 and 18 μm, morepreferably between 14 and 16 μm, W₃ is between 6 and 9 μm, morepreferably between 7 and 8 μm, and R_(3MID) is between 10 and 12 μm,more preferably between 11 and 12 μm. The HHPW3 is between 6 and 8 μm.

The fourth set of embodiments have: lambda zero (zero dispersionwavelength) less than 1350 nm, preferably between 1290 and 1350 nm, morepreferably between 1290 and 1330; dispersion at 1310 nm between −5 and 5ps/nm-km, preferably between −3 and 3 ps/nm-km, and in some preferredembodiments between −2 and 2 ps/nm-km; dispersion slope at 1310 nm lessthan 0.10 ps/nm²-km; optical effective area at 1310 nm greater than 60μm², preferably greater than 65 μm²; MFD at 1310 nm greater than 9 μm;attenuation at 1310 nm of less than 0.35 dB/km, preferably less than0.34 dB/km; dispersion at 1550 nm greater than 15 ps/nm-km preferablybetween 15 and 21 ps/nm-km, more preferably between 16 and 20;dispersion slope at 1550 nm less than 0.07 ps/nm²-km, and in somepreferred embodiments between 0.060 and 0.070 ps/nm²-km; opticaleffective area at 1550 nm greater than 75 μm², preferably greater than80 μm², and in some preferred embodiments between 80 and 95 μm²; MFD at1550 nm greater than 10 μm, and in some preferred embodiments between 10and 11 μm; attenuation at 1550 nm of less than 0.20 dB/km, preferablyless than 0.19 dB/km. In some embodiments, the cable cutoff is less than1500 nm, and in other embodiments between 1300 and 1500 nm. Preferably,the pin array loss at 1550 nm is less than 25 dB, more preferably lessthan 20 dB. Preferably the lateral load loss at 1550 nm is less than 2dB/m, more preferably less than 1 dB/m. Preferably the fiber cutoff isless than 1650, more preferably less than 1550 nm.

Optical waveguide fibers are disclosed herein comprising: a centralsegment extending radially outwardly from a centerline to radius R₁ andhaving a positive relative refractive index percent, Δ₁(r) in %, whereinthe central segment has a maximum relative refractive index percent,Δ_(1MAX), greater than 0.3%; an anular segment surrounding the centralcore region and extending to a radius R₃ and having a negative relativerefractive index percent, Δ₃(r) in %, with a minimum relative refractiveindex percent, Δ_(3MIN); and an outer annular cladding surrounding theannular region and having a relative refractive index percent, Δ_(c)(r)in %; wherein Δ_(1MAX)>0>Δ_(3MIN); and wherein the relative refractiveindex of the optical fiber is selected to provide an effective area ofgreater than about 75 μm² at a wavelength of about 1550 nm, a dispersionslope of less than 0.07 ps/nm²/km at a wavelength of about 1550 nm, azero-dispersion wavelength of less than 1350 nm, and an attenuation ofless than 0.20 dB/km at a wavelength of about 1550 nm. Preferably, thecentral segment has an outermost radius, R₁, between 4 and 8 μm.Preferably, the annular segment has a width W₃ between 3 and 14 μm, amidpoint R_(3MID) between 10 and 20 μm, and an outermost radius R₃between 11 and 27 μm. Preferably, the optical fiber has a MFD greaterthan about 10 μm at a wavelength of about 1550 nm. Preferably, theoptical fiber has a dispersion of between −5 and 5 ps/nm-km at awavelength of about 1310 nm, and a dispersion slope of less than 0.10ps/nm²-km at a wavelength of about 1310 nm. Preferably, the opticalfiber has an effective area of greater than 60 μm² at a wavelength ofabout 1310 nm, and in some preferred embodiments the effective area isgreater than 80 μm² at a wavelength of about 1310 nm. Preferably, theoptical fiber has an attenuation of less than 0.35 dB/km at a wavelengthof about 1310 nm. Preferably, the optical fiber has a cabled cutoffwavelength of less than 1500 nm. Preferably, the pin array loss of theoptical fiber is less than 25 dB.

In one subset of optical fibers, the annular segment is directlyadjacent to the central segment.

In another subset, the optical fibers further comprise an intermediateannular segment disposed between the central segment and the annularsegment, and preferably the intermediate annular segment surrounds anddirectly abuts the central segment, and preferably the annular segmentsurrounds and directly abuts the intermediate annular segment.Preferably, the intermediate annular segment has a maximum relativerefractive index, Δ_(2MAX), wherein |Δ_(2MAX)|<0.05%. Preferably, theintermediate annular segment has a width W₂ between 1 and 8 μm, amidpoint R_(2MID) between 7 and 11 μm, and an outermost radius, R₂,between 6 and 15 μm.

Preferably, the outer anular cladding directly abuts the annular region.

An optical fiber communication system is disclosed herein comprising atransmitter, a receiver, and an optical fiber transmission linecomprising the optical fiber disclosed herein and a second optical fiberhaving a negative dispersion at a wavelength of about 1550 nm.

Optical waveguide fiber is disclosed herein comprising: a centralsegment extending radially outwardly from a centerline to a radius R₁and having a positive relative refractive index percent, Δ₁(r) in %,wherein the central segment has a maximum relative refractive indexpercent, Δ_(1MAX), greater than 0.3%; an intermediate annular segmentsurrounding and directly adjacent to the central segment, wherein theintermediate annular segment has a maximum relative refractive index,Δ_(2MAX), wherein |Δ_(2MAX)|<0.05%, and wherein the intermediate annularsegment has a width W₂ between 1 and 8 μm, a midpoint R_(2MID) between 7and 11 μm, and an outermost radius, R₂, between 6 and 15 μm; an annularsegment surrounding and directly adjacent to the intermediate annularsegment and extending to a radius R₃ and having a negative relativerefractive index percent, Δ₃(r) in %, with a minimum relative refractiveindex percent, Δ_(3MIN); and an outer annular cladding surrounding theannular region and having a relative refractive index percent, Δ_(c) (r)in %; wherein Δ_(1MAX)>0>Δ_(3MIN); wherein the relative refractive indexof the optical fiber is selected to provide an effective area of greaterthan about 75 μm² at a wavelength of about 1550 nm, a dispersion slopeof less than 0.07 ps/nm²/km at a wavelength of about 1550 nm, azero-dispersion wavelength of less than 1350 nm, and an attenuation ofless than 0.20 dB/km at a wavelength of about 1550 nm.

Optical waveguide fiber is also disclosed herein comprising: a centralsegment extending radially outwardly from a centerline to a radius R₁and having a positive relative refractive index percent, Δ₁(r) in %,wherein the central segment has a maximum relative refractive indexpercent, Δ_(1MAX), greater than 0.5%; an annular segment surrounding anddirectly adjacent to the central segment and extending to a radius R₃and having a negative relative refractive index percent, Δ₃(r) in %,with a minimum relative refractive index percent, Δ_(3MIN); and an outerannular cladding surrounding the annular region and having a relativerefractive index percent, Δ_(c) (r) in %; wherein Δ_(1MAX)>0>Δ_(3MIN);wherein the relative refractive index of the optical fiber is selectedto provide an effective area of greater than about 75 μm² at awavelength of about 1550 nm, a dispersion slope of less than 0.07ps/nm²/km wavelength of about 1550 nm, a zero-dispersion wavelength ofless than, 1350 nm, and an attenuation of less than 0.20 dB/km at awavelength of about 1550 nm.

Preferably, the optical fiber disclosed herein is capable oftransmitting optical signals in the 1260 nm to 1650 nm wavelength range.

Preferably, the fibers disclosed herein are made by a vapor depositionprocess. Even more preferably, the fibers disclosed herein are made byan outside vapor deposition (OVD) process. Thus, for example, known OVDlaydown, consolidation, and draw techniques may be advantageously usedto produce the optical waveguide fiber disclosed herein. Otherprocesses, such as modified chemical vapor deposition (MCVD) or vaporaxial deposition (VAD) or plasma chemical vapor deposition (PCVD) may beused. Thus, the refractive indices and the cross sectional profile ofthe optical waveguide fibers disclosed herein can be accomplished usingmanufacturing techniques known to those skilled in the art including,but in no way limited to, OVD, VAD and MCVD processes.

FIG. 4 is a schematic representation (not to scale) of an opticalwaveguide fiber 100 as disclosed herein having core 101 and an outerannular cladding or outer cladding layer or clad layer 200 directlyadjacent and surrounding the core 101. The core 101 has multiplesegments (not shown in FIG. 4).

Preferably, the cladding contains no germania or fluorine dopantstherein. More preferably, the cladding 200 of the optical fiberdisclosed herein is pure or substantially pure silica. The clad layer200 may be comprised of a cladding material which was deposited, forexample during a laydown process, or which was provided in the form of ajacketing, such as a tube in a rod-in-tube optical preform arrangement,or a combination of deposited material and a jacket. The clad layer 200may include one or more dopants. The clad layer 200 is surrounded by aprimary coating P and a secondary coating S. The refractive index of thecladding 200 is used to calculate the relative refractive indexpercentage as discussed elsewhere herein.

Referring to the Figures, the clad layer 200 has a refractive index ofn_(c) surrounding the core having a Δ(r)=0%.

Preferably, the optical fiber disclosed herein has a silica-based coreand cladding. In preferred embodiments, the cladding has an outerdiameter, 2*Rmax, of about 125 μm. Preferably, the outer diameter of thecladding has a constant diameter along the length of the optical fiber.In preferred embodiments, the refractive index of the optical fiber hasradial symmetry. Preferably, the outer diameter of the core has aconstant diameter along the length of the optical fiber. Preferably, oneor more coatings surround and are in contact with the cladding. Thecoating is preferably a polymer coating such as acrylate. Preferably thecoating has a constant diameter, radially and along the length of thefiber.

As shown in FIG. 5, an optical fiber 100 as disclosed herein may beimplemented in an optical fiber communication system 330. System 330includes a transmitter 334 and a receiver 336, wherein optical fiber 100allows transmission of an optical signal between transmitter 334 andreceiver 336. System 330 is preferably capable of 2-way communication,and transmitter 334 and receiver 336 are shown for illustration only.The system 330 preferably includes a link which has a section or a spanof optical fiber as disclosed herein. The system 330 may also includeone or more optical devices optically connected to one or more sectionsor spans of optical fiber as disclosed herein, such as one or moreregenerators, amplifiers, or dispersion compensating modules. In atleast one preferred embodiment, an optical fiber communication systemaccording to the present invention comprises a transmitter and receiverconnected by an optical fiber without the presence of a regeneratortherebetween. In another preferred embodiment, an optical fibercommunication system according to the present invention comprises atransmitter and receiver connected by an optical fiber without thepresence of an amplifier therebetween. In yet another preferredembodiment, an optical fiber communication system according to thepresent invention comprises a transmitter and receiver connected by anoptical fiber having neither an amplifier nor a regenerator nor arepeater therebetween.

Preferably, the optical fibers disclosed herein have a low watercontent, and preferably are low water peak optical fibers, i.e. havingan attenuation curve which exhibits a relatively low, or no, water peakin a particular wavelength region, especially in the E-band.

Methods of producing low water peak optical fiber can be found in U.S.Pat. No. 6,477,305, U.S. Patent Application Publication No. 2002102083,and PCT Application Publication No. WO01/47822.

A soot preform or soot body is preferably formed by chemically reactingat least some of the constituents of a moving fluid mixture including atleast one glass-forming precursor compound in an oxidizing medium toform a silica-based reaction product. At least a portion of thisreaction product is directed toward a substrate, to form a porous silicabody, at least a portion of which typically includes hydrogen bonded tooxygen. The soot body may be formed for example, by depositing boyers ofsoot onto a bait rod via an OVD process.

A substrate or bait rod or mandrel is inserted through a glass body suchas a hollow or tubular handle and mounted on a lathe. The lathe isdesigned to rotate and translate the mandrel in close proximity with asoot-generating burner. As the mandrel is rotated and translated,silica-based reaction product, known generally as soot, is directedtoward the mandrel. At least a portion of silica-based reaction productis deposited on the mandrel and on a portion of the handle to form abody thereon.

Once the desired quantity of soot has been deposited on the mandrel,soot deposition is terminated and the mandrel is removed from the sootbody.

Upon removal of the mandrel, the soot body defines a centerline holepassing axially therethrough. Preferably, the soot body is suspended bya handle on a downfeed device and positioned within a consolidationfurnace. The end of the centerline hole remote from the handle ispreferably fitted with a bottom plug prior to positioning the soot bodywithin the consolidation furnace. Preferably, the bottom plug ispositioned and held in place with respect to the soot body by frictionfit. The plug is further preferably tapered to facilitate entry and toallow at least temporary affixing, and at least loosely, within the sootbody.

The soot body is preferably chemically dried, for example, by exposingsoot body to a chlorine-containing atmosphere at elevated temperaturewithin consolidation furnace. A chlorine-containing atmosphereeffectively removes water and other impurities from soot body, whichotherwise would have an undesirable effect on the properties of theoptical waveguide fiber manufactured from the soot body. In an OVDformed soot body, the chlorine flows sufficiently through the soot toeffectively dry the entire preform, including the centerline regionsurrounding centerline hole.

Following the chemical drying step, the temperature of the furnace iselevated to a temperature sufficient to consolidate the soot blank intoa sintered glass preform, preferably about 1500° C. The centerline holeis then closed during the consolidation step so that the centerline holedoes not have an opportunity to be rewetted by a hydrogen compound priorto centerline hole closure. Preferably, the centerline region has aweighted average OH content of less than about 1 ppb.

Exposure of the centerline hole to an atmosphere containing a hydrogencompound can thus be significantly reduced or prevented by closing thecenterline hole during consolidation.

As described above and elsewhere herein, the plugs are preferably glassbodies having a water content of less than about 31 ppm by weight, suchas fused quartz plugs, and preferably less than 5 ppb by weight, such aschemically dried silica plugs. Typically, such plugs are dried in achlorine-containing atmosphere, but an atmosphere containing otherchemical drying agents are equally applicable. Ideally, the glass plugswill have a water content of less than 1 ppb by weight. In addition, theglass plugs are preferably thin walled plugs ranging in thickness fromabout 200 μm to about 2 mm. Even more preferably, at least a portion ofa top plug has a wall thickness of about 0.2 to about 0.5 mm. Morepreferably still, elongated portion 66 has a wall thickness of about 0.3mm to about 0.4 mm. Thinner walls promote diffusion, but are moresusceptible to breakage during handling.

Thus, inert gas is preferably diff-used from the centerline hole afterthe centerline hole has been sealed to create a passive vacuum withinthe centerline hole, and thin walled glass plugs can facilitate rapiddiffusion of the inert gas from the centerline hole. The thinner theplug, the greater the rate of diffusion. A consolidated glass preform ispreferably heated to an elevated temperature which is sufficient tostretch the glass preform, preferably about 1950° C. to about 2100° C.,and thereby reduce the diameter of the preform to form a cylindricalglass body, such as a core cane or an optical fiber, wherein thecenterline hole collapses to form a solid centerline region. The reducedpressure maintained within the sealed centerline hole created passivelyduring consolidation is generally sufficient to facilitate completecenterline hole closure during the draw (or redraw) process.Consequently, overall lower O—H overtone optical attenuation can beachieved. For example, the water peak at 1383 nm, as well as at other OHinduced water peaks, such as at 950 nm or 1240 nm, can be lowered, andeven virtually eliminated.

A low water peak generally provides lower attenuation losses,particularly for transmission signals between about 1340 nm and about1470 nm. Furthermore, a low water peak also affords improved pumpefficiency of a pump light emitting device which is optically coupled tothe optical fiber, such as a Raman pump or Raman amplifier which mayoperate at one or more pump wavelengths. Preferably, a Raman amplifierpumps at one or more wavelengths which are about 100 nm lower than anydesired operating wavelength or wavelength region. For example, anoptical fiber carrying an operating signal at wavelength of around 1550nm may be pumped with a Raman amplifier at a pump wavelength of around1450 nm. Thus, the lower fiber attenuation in the wavelength region fromabout 1400 nm to about 1500 nmn would tend to decrease the pumpattenuation and increase the pump efficiency, e.g. gain per mW of pumppower, especially for pump wavelengths around 1400 nm. Generally, forgreater OH impurities in a fiber, the water peak grows in width as wellas in height. Therefore, a wider choice of more efficient operation,whether for operating signal wavelengths or amplification with pumpwavelengths, is afforded by the smaller water peak. Thus, reducing OHimpurities can reduce losses between, for example, for wavelengthsbetween about 1260 nm to about 1650 nm, and in particular reduced lossescan be obtained in the 1383 nm water peak region thereby resulting inmore efficient system operation.

The fibers disclosed herein exhibit low PMD values particularly whenfabricated with OVD processes. Spinning of the optical fiber may alsolower PMD values for the fiber disclosed herein.

All of the optical fibers disclosed herein can be employed in an opticalsignal transmission system, which preferably comprises a transmitter, areceiver, and an optical transmission line. The optical transmissionline is optically coupled to the transmitter and receiver. The opticaltransmission line preferably comprises at least one optical fiber span,which preferably comprises at least one section of the optical fiberdisclosed herein. The optical transmission line may also comprise asection of a second optical fiber having a negative dispersion-at awavelength of about 1550 nm, for example to effect dispersioncompensation within the optical transmission line.

FIG. 6 schematically illustrates another embodiment of an optical fibercommunication system 400 disclosed herein. System 400 includes atransmitter 434 and a receiver 436 which are optically connected byoptical transmission line 440. Optical transmission line 440 comprises afirst fiber 442 which is a low attenuation large effective area opticalfiber as disclosed herein, and a second optical fiber 444 having adispersion at 1550 nm of between −70 and −150 ps/nm-km. In preferredembodiments, the second fiber has a relative refractive index profilehaving a central core segment with a positive relative refractive index,a moat segment surrounding and in contact with the central segment andhaving a negative relative refractive index, and a ring segmentsurrounding and in contact with the moat segment and having a positiverelative refractive index. Preferably, the central segment of the secondfiber has a maximum relative refractive index between 1.6% and 2%, themoat segment has a minimum relative refractive index between −0.25% and−0.44%, and the ring segment has a maximum relative, refractive indexbetween 0.2% and 0.5%. Preferably, the central segment of the secondfiber has an outer radius of between 1.5 and 2 μm, the moat segment hasan outer radius of between 4 and 5 μm, and the ring segment has amidpoint between 6 and 7 μm. An example of a second fiber is describedin U.S. Patent Application Publication No. 2003/0053780, Ser. No.10/184,377 published on Mar. 20, 2003, such as depicted in FIG. 4 orFIG. 6 therein. The first fiber 442 and second fiber 444 may beoptically connected by a fusion splice, an optical connector or thelike, as depicted by the symbol “X” in FIG. 6. Preferably, the kappa ofthe first fiber, k1, is matched to the kappa of the second fiber, k2,wherein k1/k2 is preferably between 0.8 and 1.2, more preferably between0.9 and 1.1, and even more preferably between 0.95 and 1.05. The opticaltransmission line 440 may also comprise one or more components and/orother optical fiber(s) (for example one or more “pigtail fibers” 445 atjunctions between fibers and/or components). In preferred embodiments,at least a portion of the second optical fiber 444 is optionallydisposed within a dispersion compensating module 446. Opticaltransmission line 440 allows transmission of an optical signal betweentransmitter 434 and receiver 436. Preferably, the residual dispersion inthe optical transmission line is less than about 5 ps/nm per 100 km offiber.

The system preferably further-comprises at least one amplifier, such asa Raman amplifier, optically coupled to the optical fiber section.

The system further preferably comprises a multiplexer forinterconnecting a plurality of channels capable of carrying opticalsignals onto the optical transmission line, wherein at least one, morepreferably at least three, and most preferably at least ten opticalsignals propagate at a wavelength between about 1260 nm and 1625 nm.Preferably, at least one signal propagates in one or more of thefollowing wavelength regions: the 1310 nm band, the E-band, the S-band,the C-band, and the L-band.

In some preferred embodiments, the system is capable of operating in acoarse wavelength division multiplex mode wherein one or more signalspropagate in at least one, more preferably at least two of the followingwavelength regions: the 1310 nm band, the E-band, the S-band, theC-band, and the L-band. In one preferred embodiment, the system operatesat one or more wavelengths between 1530 and 1565 nm.

In one preferred embodiment, the system comprises a section of opticalfiber as disclosed herein having a length of not more than 20 km. Inanother preferred embodiment, the systems comprises a section of opticalfiber as disclosed herein having a length of greater than 20 km. In yetanother preferred embodiment, the system comprises a section of opticalfiber as disclosed herein having length of greater than 70 km.

In one preferred embodiment, the system operates at less than or equalto about 1 Gbit/s. In another preferred embodiment, the system operatesat less than or equal to about 2 Gbit/s. In yet another preferredembodiment, the system operates at less than or equal to about 10Gbit/s. In still another preferred embodiment, the system operates atless than or equal to about 40 Gbit/s. In yet another preferredembodiment, the system operates at greater than or equal to about 40Gbit/s.

In a preferred embodiment, a system disclosed herein comprises anoptical source, an optical fiber as disclosed herein optically coupledto the optical source, and a receiver optically coupled to the opticalfiber for receiving the optical signals transmitted through the opticalfiber, the optical source having the capability of dithering, and/orphase modulating, and/or amplitude modulating, the optical signalgenerated by the optical source, and the optical signal is received bythe receiver.

It is to be understood that the foregoing description is exemplary ofthe invention only and is intended to provide an overview for theunderstanding of the nature and character of the invention as it isdefined by the claims. The accompanying drawings are included to providea further understanding of the invention and are incorporated andconstitute part of this specification. The drawings illustrate variousfeatures and embodiments of the invention which, together with theirdescription, serve to explain the principals and operation of theinvention. It will become apparent to those skilled in the art thatvarious modifications to the preferred embodiment of the invention asdescribed herein can be made without departing from the spirit or scopeof the invention as defined by the appended claims.

1. An optical waveguide fiber comprising: a central segment extendingradially outwardly from a centerline to a radius R₁ and having apositive relative refractive index percent, Δ₁(r) in %, wherein thecentral segment has a maximum relative refractive index percent,Δ_(1MAX); an intermediate annular segment surrounding and directlyadjacent to the central segment; and an outer annular segmentsurrounding and directly adjacent to the intermediate annular segmentand extending to a radius R₃ and having a negative relative refractiveindex percent, Δ₃(r) in %, with a minimum relative refractive indexpercent, Δ_(3MIN), less than −0.1%; and an outer annular claddingsurrounding and directly adjacent to the outer annular segment; whereinthe relative refractive index of the optical fiber provides a dispersionslope of less than 0.07 ps/nm²/km at a wavelength of 1550 nm, azero-dispersion wavelength of less than 1350 nm, and an attenuation ofless than 0.20 dB/km at a wavelength of 1550 nm.
 2. The optical fiber ofclaim 1 wherein the intermediate annular segment has a relativerefractive index profile, Δ₂(r), having a maximum absolute magnitude,and Δ_(1MAX) is greater than the maximum absolute magnitude of Δ₂(r),and the maximum absolute magnitude of Δ₂(r) is greater than Δ_(3MIN). 3.The optical fiber of claim 2 wherein the maximum absolute magnitude ofΔ₂(r) is less than 0.05%.
 4. The optical fiber of claim 2 whereinΔ_(1MAX) is greater than 0.3%.
 5. The optical fiber of claim 2 whereinΔ_(1MAX) is less than 0.5%.
 6. The optical fiber of claim 2 whereinΔ_(1MAX) is between 0.3% and 0.5%.
 7. The optical fiber of claim 2wherein the intermediate annular segment extends to a radius R₂ of lessthan 10 μm.
 8. The optical fiber of claim 2 wherein the outer annularsegment has a width, W₃, less than 7 μm.
 9. The optical fiber of claim 2wherein the outer annular segment has a width, W₃, between 3 and 7 μm.10. The optical fiber of claim 2 wherein the outer annular segmentextends to a radius, R₃, less than 17 μm.
 11. The optical fiber of claim2 wherein the outer annular segment has a midpoint R_(3MID) between 10and 13 μm.
 12. The optical fiber of claim 2 wherein the outer annularsegment has a midpoint R_(3MID) between 11 and 12 μm.
 13. The opticalfiber of claim 2 wherein the zero-dispersion wavelength is between 1290and 1330 nm.
 14. The optical fiber of claim 2 wherein the optical fiberhas an attenuation at 1380 nm and an attenuation at 1310 nm, and theattenuation at 1380 nm is not more than 0.1 dB/km greater than theattenuation at 1310 nm.
 15. The optical fiber of claim 2 wherein theoptical fiber has an attenuation at 1380 nm and an attenuation at 1310nm, and the attenuation at 1380 nm is less than the attenuation at 1310nm.
 16. The optical fiber of claim 2 wherein the optical fiber has alateral load loss at 1550 nm of less than 2 dB/m.
 17. The optical fiberof claim 2 wherein the optical fiber has a lateral load loss at 1550 mmof less than 1 dB/m.
 18. The optical fiber of claim 2 wherein theattenuation at a wavelength of 1550 nm is less than 0.19 dB/km.
 19. Anoptical waveguide fiber comprising: a central segment extending radiallyoutwardly from a centerline to a radius R₁ and having a positiverelative refractive index percent, Δ₁(r) in %, wherein the centralsegment has a maximum relative refractive index percent, Δ_(1MAX), lessthan 0.5%; an intermediate annular segment surrounding and directlyadjacent to the central segment, wherein the intermediate annularsegment extends to a radius R₂ of less than 10 μm; and an outer annularsegment surrounding and directly adjacent to the intermediate annularsegment and extending to a radius R₃ and having a negative relativerefractive index percent, A₃(r) in %, with a minimum relative refractiveindex percent, Δ_(3MIN), less than −0.1%; and an outer annular claddingsurrounding and directly adjacent to the outer annular segment; whereinthe relative refractive index of the optical fiber provides a dispersionat a wavelength of 1550 nm of between 16 and 20 ps/nm/km, a dispersionslope of less than 0.07 ps/nm²/km at a wavelength of 1550 nm.
 20. Theoptical fiber of claim 19 wherein the intermediate annular segment has arelative refractive index profile, Δ₂(r), having a maximum absolutemagnitude, and Δ_(1MAX) is greater than the maximum absolute magnitudeof Δ₂(r), and the maximum absolute magnitude of Δ₂(r) is greater thanΔ_(3MIN).
 21. The optical fiber of claim 20 wherein the maximum absolutemagnitude of Δ₂(r) is less than 0.05%.
 22. The optical fiber of claim 20wherein Δ_(1MAX), is greater than 0.3% and less than 0.5%.
 23. Theoptical fiber of claim 20 wherein the outer annular segment has a width,W₃, less than 7 μm.
 24. The optical fiber of claim 20 wherein the outerannular segment has a width, W₃, between 3 and 7 μm.
 25. The opticalfiber of claim 20 wherein the outer annular segment extends to a radius,R₃, less than 17 μm.
 26. The optical fiber of claim 20 wherein the outerannular segment has a midpoint R_(3MID) between 10 and 13 μm.
 27. Theoptical fiber of claim 20 wherein the outer annular segment has amidpoint R_(3MID) between 11 and 12 μm.
 28. The optical fiber of claim20 wherein the zero-dispersion wavelength is between 1290 and 1330 nm.29. The optical fiber of claim 20 wherein the optical fiber has anattenuation at 1380 nm and an attenuation at 1310 nm, and theattenuation at 1380 nm is not more than 0.1 dB/km greater than theattenuation at 1310 nm.
 30. The optical fiber of claim 20 wherein theoptical fiber has an attenuation at 1380 nm and an attenuation at 1310nm, and the attenuation at 1380 nm is less than the attenuation at 1310nm.
 31. The optical fiber of claim 20 wherein the optical fiber has alateral load loss at 1550 nm of less than 2 dB/m.
 32. The optical fiberof claim 20 wherein the optical fiber has a lateral load loss at 1550 nmof less than 1 dB/m.
 33. The optical fiber of claim 20 wherein theattenuation at a wavelength of 1550 nm is less than 0.19 dB/km.